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A003190 Number of connected 2-plexes.
(Formerly M3121)
1
1, 0, 1, 3, 29, 2101, 7011181, 1788775603301, 53304526022885278403, 366299663378889804782330207902, 1171638318502622784366970315262493034215728, 3517726593606524901243694560022510194169866584119717555335 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

The Palmer reference (incorrectly) has a(7)=7011349, a(8)=1788775603133, a(9)=53304526022885278659. - Sean A. Irvine, Mar 05 2015

Also connected 3-uniform hypergraphs on n vertices. - Gus Wiseman, Feb 23 2019

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..12.

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

E. M. Palmer, On the number of n-plexes, Discrete Math., 6 (1973), 377-390.

FORMULA

Inverse Euler transform of A000665. - Sean A. Irvine, Mar 05 2015

EXAMPLE

From Gus Wiseman, Feb 23 2019: (Start)

Non-isomorphic representatives of the a(5) = 29 2-plexes:

  {{125}{345}}

  {{123}{245}{345}}

  {{135}{245}{345}}

  {{145}{245}{345}}

  {{123}{145}{245}{345}}

  {{124}{135}{245}{345}}

  {{125}{135}{245}{345}}

  {{134}{235}{245}{345}}

  {{145}{235}{245}{345}}

  {{123}{124}{135}{245}{345}}

  {{123}{145}{235}{245}{345}}

  {{124}{134}{235}{245}{345}}

  {{134}{145}{235}{245}{345}}

  {{135}{145}{235}{245}{345}}

  {{145}{234}{235}{245}{345}}

  {{123}{124}{134}{235}{245}{345}}

  {{123}{134}{145}{235}{245}{345}}

  {{123}{145}{234}{235}{245}{345}}

  {{124}{135}{145}{235}{245}{345}}

  {{125}{135}{145}{235}{245}{345}}

  {{135}{145}{234}{235}{245}{345}}

  {{123}{124}{135}{145}{235}{245}{345}}

  {{124}{135}{145}{234}{235}{245}{345}}

  {{125}{135}{145}{234}{235}{245}{345}}

  {{134}{135}{145}{234}{235}{245}{345}}

  {{123}{124}{135}{145}{234}{235}{245}{345}}

  {{125}{134}{135}{145}{234}{235}{245}{345}}

  {{124}{125}{134}{135}{145}{234}{235}{245}{345}}

  {{123}{124}{125}{134}{135}{145}{234}{235}{245}{345}}

(End)

CROSSREFS

Column k=3 of A301924.

Cf. A000665 (unlabeled 3-uniform), A025035, A125791 (labeled 3-uniform), A289837, A301922, A302374 (labeled 3-uniform spanning), A302394, A306017, A319540, A320395, A322451 (unlabeled 3-uniform spanning), A323292-A323299.

Sequence in context: A182385 A255597 A319637 * A322451 A213792 A133663

Adjacent sequences:  A003187 A003188 A003189 * A003191 A003192 A003193

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(7)-a(9) corrected and extended by Sean A. Irvine, Mar 05 2015

STATUS

approved

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Last modified April 1 02:15 EDT 2020. Contains 333153 sequences. (Running on oeis4.)